1. Field of the Invention
The present invention relates to a light emitting device, and more particularly, to a light emitting device including a light emitting element, a bonding wire, a lead, and a package.
2. Description of the Related Art
As disclosed in Japanese Patent No. 5471244, the applicant of the present invention has developed a lighting device including a first lead having a mounting area in which a light emitting diode (LED) chip is mounted on the surface side thereof and exposing the rear surface side thereof, a second lead having a boning area to which a wire from the LED chip is bonded on the surface side thereof and exposing the rear surface side thereof, and a packaging resin portion surrounding the first lead and the second lead and forming an insulating area between the first lead and the second lead, in which a portion of the first lead facing the second lead is a small-thickness portion, the LED chip is mounted on the surface side of the small-thickness portion, a resin material of the packaging resin portion goes around to the rear surface side of the small-thickness portion, a portion of the second lead facing the first lead is a small-thickness portion, and the resin material of the packaging resin portion goes around to the rear surface side of the small-thickness portion.
It is preferable that the thickness of the first lead and the second lead in Japanese Patent No. 5471244 be set to be large for the purpose of promotion of heat dissipation and improvement in rigidity.
The first lead and the second lead are formed of a single metal sheet by press punching for the purpose of improvement in productivity, but the distance between an edge of the small-thickness portion in the first lead and an edge of the small-thickness portion in the second lead is defined by a width of a punch of a press punching machine. Accordingly, the larger the thickness of the leads becomes, the larger the distance becomes.
The LED chip is mounted on the first lead and the bonding wire from the LED chip is bonded to a bonding area on the surface side of the second lead.
Accordingly, when the distance becomes larger, the length of the bonding wire becomes larger, the volume of a sealing resin filled below the bonding wire becomes larger, expansion/contraction of the sealing resin due to heat becomes larger, and a stress applied to the bonding wire from the sealing resin becomes larger. As a result, there is a problem in that metal fatigue of the bonding wire increase to easily cause disconnection failure.